Blender renders in color, but I can't see the color when I edit
On the top right hand of the viewport there are four orbs.
(From Left-Right):

Wireframe. This shows the wireframes of all your objects so you can better understand the geometry they have.
Viewport Shading. This shades everything a gray color. This mode is intended to provide the artist a good view of the scene geometry and is very smooth and fast.
Texture Preview. This mode allows you to preview the texture first without actually using the render engine. It's very useful for designing materials.
Rendered View. This will allow you to view the scene using the actual render engine. What you see here will also be what you see when you actually render the scene.

Simply click the orbs to change the shading mode.
Most of the time you should be using Viewport Shading because it is fast and allows you to work quickly.